special marker and keyword in SQL indicating that something has no value
Factsheet
Null (SQL)
Notation ω
Null (SQL)
Notation ω
Wikipedia
en.wikipedia.org › wiki › Null_(SQL)
Null (SQL) - Wikipedia
1 day ago - In an Oracle RDBMS, for example, ... Since Null is not a member of any data domain, it is not considered a "value", but rather a marker (or placeholder) indicating the undefined value....
HistoryNull propagationComparisons with NULL and the three-valued logic (3VL)Analysis of SQL Null missing-value semanticsCheck constraints and foreign keysOuter joinsAggregate functionsWhen two nulls are equal: grouping, sorting, and some set operationsEffect on index operationNull-handling functionsData typing of Null and UnknownBOOLEAN data typeControversyFurther reading
Oracle
docs.oracle.com › en › database › other-databases › timesten › 22.1 › sql-reference › null-values.html
Null Values
July 25, 2025 - The value NULL indicates the absence of a value. It is a placeholder for a value that is missing. Use a NULL when the actual value is not known or when a value would not be meaningful. Do not use NULL to represent a numeric value of zero, because they are not equivalent.
Null in SQL ,what does it store
Null is a state, not a value. It doesn’t store nothing, it is not nothing, it is not equal to itself. It indicates that we do not know, or cannot know, or perhaps that nothing can be known. Null isn’t not, but isn’t not not, nor is it. tl;dr - “there is no value recorded” More on reddit.com
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June 24, 2025What is NULL in SQL? - Stack Overflow
I am confuse about what is the value of NULL in SQL. NULL I think is empty. So will it contain any garbage value or unknown value or like 0 in integer or blank in character? More on stackoverflow.com
[Oracle SQL] How can I return a specific row if no rows are retrieved in my query?
Sounds to me like you want to return a default value. My SQL is rusty but I think you need a conditional statement or 3 with the EXISTS() function. Of course the real question is, why are you doing this in SQL and not whatever language you are programming the rest of your app in. More on reddit.com
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January 14, 2019[ORACLE] Selecting a null value to an integer variable but an "if (A = null) then..." statement wont run
To be clear 'A' is a variable defined as an integer . Another sql statement selects an auto key value(produced by a sequence command) and the goals is to run the SQL anytime the return is a null value on the auto key value. The SQL statement creates a record on a particular table with certain values pulled from various tables, all related to each other through various auto key (sequence) values.
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April 24, 2014Oracle
docs.oracle.com › en › database › oracle › oracle-database › 19 › sqlrf › Nulls.html
SQL Language Reference
November 12, 2025 - If a column in a row has no value, then the column is said to be null, or to contain null. Nulls can appear in columns of any data type that are not restricted by NOT NULL or PRIMARY KEY integrity constraints. Use a null when the actual value is not known or when a value would not be meaningful.
GeeksforGeeks
geeksforgeeks.org › sql › sql-null-values
NULL values in SQL - GeeksforGeeks
January 5, 2026 - Since it is often not possible to determine which interpretation applies, SQL treats all NULL values as distinct and does not distinguish between them. Typically, it can have one of three interpretations: Value Unknown: The value exists but is not known. Value Not Available: The value exists but is intentionally withheld. Attribute Not Applicable: The value is undefined for a specific record. Setting a NULL value is appropriate when the actual value is unknown, or when a value is not meaningful.
Oracle
docs.oracle.com › database › 121 › SQLRF › sql_elements005.htm
Nulls
If you use any other condition with nulls and the result depends on the value of the null, then the result is UNKNOWN. Because null represents a lack of data, a null cannot be equal or unequal to any value or to another null. However, Oracle considers two nulls to be equal when evaluating a DECODE function. Refer to DECODE for syntax and additional information.
Modern SQL
modern-sql.com › concept › null
Modern SQL: NULL — purpose, comparisons, NULL in expressions, mapping to/from NULL
Expressions and functions that process a null value generally return the null value.4 Noteworthy exceptions are aggregate functions and—due to the three-valued logic of SQL—two logical operations.5 · The result of the following expressions is therefore null: ... The Oracle database treats an empty string as null and vice versa: on the one hand, '' IS NULL is true, on the other hand is null treated as an empty string in string concatenations (||).
IONOS UK
ionos.co.uk › digital guide › server › configuration › sql nvl
How to use SQL NVL - IONOS UK
February 26, 2025 - The function checks the records ... information you’ve indicated. NULL values usually represent a lack of data in a row or column. They are not the same as the numerical value ‘0’ or spaces.
W3Schools
w3schools.com › sql › sql_null_values.asp
SQL NULL Values - IS NULL and IS NOT NULL
The IS NULL operator is used to test for empty values (NULL values). The following SQL lists all customers with a NULL value in the "Address" field:
Oracle
docs.oracle.com › en › database › other-databases › nosql-database › 25.3 › sqlreferencefornosql › is-null-and-is-not-null-operators.html
IS NULL and IS NOT NULL Operators
February 6, 2026 - The IS NULL operator tests whether the result of its input expression is NULL. If the input expression returns more than one item, an error is raised. If the result of the input expression is empty, IS NULL returns false. Otherwise, IS NULL returns true if and only if the single item computed ...
DB Vis
dbvis.com › thetable › dealing-with-null-in-sql-complete-guide
Dealing With NULL in SQL: Complete Guide
April 9, 2025 - In SQL, NULL represents missing or unknown values in a database table. Unlike zero or an empty string, NULL signifies the absence of a value–not zero, not an empty string, but a true unknown or undefined value.
Oracle-Base
oracle-base.com › articles › misc › null-related-functions
NULL-Related Functions - ORACLE-BASE
Instead they must use the IS NULL or IS NOT NULL operators. SQL> SELECT * FROM null_test_tab WHERE col1 IS NULL ORDER BY id; ID COL1 COL2 COL3 COL4 ---------- ---------- ---------- ---------- ---------- 2 TWO THREE FOUR 3 THREE FOUR 4 THREE THREE 3 rows selected. SQL> The NVL function allows you to replace null values with a default value.
Reddit
reddit.com › r/sql › null in sql ,what does it store
r/SQL on Reddit: Null in SQL ,what does it store
June 24, 2025 -
What do null in sql store
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Null is a state, not a value. It doesn’t store nothing, it is not nothing, it is not equal to itself. It indicates that we do not know, or cannot know, or perhaps that nothing can be known. Null isn’t not, but isn’t not not, nor is it. tl;dr - “there is no value recorded”
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Null is the lack of information or the none existence of it. Let's say for example you made a shopping list and as you went round the shop you were writing the price down. Let's say dragon fruit is on your list and the shop doesn't sell it then it would have a price of "null". It doesn't mean dragon fruit has a price of "nothing" it means we don't have information or it doesn't exist.
Medium
medium.com › @DigitalFootprints › how-to-handle-null-values-in-oracle-database-a4110bf8243a
How to handle NULL values in Oracle database | by BK | Medium
September 20, 2023 - When the expression is equal to the value, it would return the value. If no match is found, then it returns default. If there is no default argument, then it returns NULL.
DZone
dzone.com › data engineering › databases › null in oracle
NULL in Oracle
August 17, 2023 - Due to the peculiarities of the three-valued logic, NOT IN is not friendly with NULLs at all: as soon as NULL gets into the selection conditions, do not wait for the data. Here Oracle deviates from the ANSI SQL standard and declares the equivalence of NULL and the empty string.
TechOnTheNet
techonthenet.com › oracle › isnull.php
Oracle / PLSQL: IS NULL Condition
If expression is not a NULL value, the condition evaluates to FALSE. Here is an example of how to use the Oracle IS NULL condition in a SELECT statement: SELECT * FROM suppliers WHERE supplier_name IS NULL; This Oracle IS NULL example will return all records from the suppliers table where the supplier_name contains a null value.
Tutorialspoint
tutorialspoint.com › sql › sql-null-values.htm
SQL - NULL Values
SQL uses the term NULL to represent a non-existent data value in the database. These values are not the same as an empty string or a zero. They don't hold any space in the database and are used to signify the absence of a value or the unknown value
Hightouch
hightouch.com › sql-dictionary › sql-is-null
SQL IS NULL - Syntax, Use Cases, and Examples | Hightouch
December 29, 2023 - A NULL value in a database represents the absence of data, and the IS NULL operator is used to identify and select rows that contain NULL values in a particular column. You would use the SQL IS NULL operator when you need to filter data from ...
LearnSQL.com
learnsql.com › blog › what-is-null-in-sql
What Is a NULL in SQL? | LearnSQL.com
March 17, 2021 - Simply put, an SQL NULL means that we don’t have a value for that particular field.
Biztory
biztory.com › home › blog › 7 things you should know about null values
7 Things to know about NULL values - Biztory | Biztory
October 25, 2025 - A NULL value is a special marker used in SQL to indicate that a data value does not exist in the database. In other words, it is just a placeholder to denote values that are missing or that we do not know.
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In simple worlds you can say that Null is not a data value, but a marker for an unknown value.
So any mathematical operations performed on NULL will result in NULL. For example,
10 + NULL = NULL
Similarly if you do string concatenation with string you get:-
'String ' || NULL || 'Concatenation' -- Result is NULL
So you can say that Null means either "not applicable" or "don't know": it is not the same as zero (0) or any other default value, but more importantly, null is treated quite differently from other values in SQL, because it literally has no value.
An example to explain what it means when we say that NULL means UNKNOWN VALUE:
StudentName TestResult
X 78
A 89
B 67
C NULL
So you can see that the student C got NULL marks in the test. So what does that mean?
Now one can say that the student does not sit in the test or it may be that the student's data is not avaialable. But it definitely does not mean that the student got 0(as if you assign 0 to the student then it would mean that the student appeared in the test and got zero) marks in the test. All we can say that the data for the student is
UNKNOWN or NULL
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A field with a NULL value is a field with no value. It is very important to understand that a NULL value is different than a zero value or a field that contains spaces.
If a column in a table is optional, we can insert a new record or update an existing record without adding a value to this column. This means that the field will be saved with a NULL value.
NULL values are treated differently from other values.
NULL is used as a placeholder for unknown or inapplicable values. Read more about this here.